Polymers and copolymers containing polymerized conjugated dienes such as butadiene are typically prepared in polymerization systems which include a solvent inert to the polymerization in which the final polymer or copolymer is at least partially soluble. This creates a problem of complete solvent removal. This invention is based on the discovery that polymers and copolymers of conjugated dienes especially those derived from butadiene have little or no solubility in propane or butane. Their use as a dispersing medium for the reaction results in easy removal due to the poor solubility of the polymer in the medium and its high vapor pressure.